Albert Einstein, 1917

Spherically closed space was Einstein's first idea of the cosmological appearance of the universe (1917):

A. Einstein, Kosmologische Betrachtungen zur allgemeinen Relativitätstheorie, (1917). English translation in "The Principle of Relativity", Dover Publications, Inc. First published in 1923. Pages 175-188.
Einstein was looking for a static solution which required the famous cosmological constant. Einstein's considerations were soon displaced by Friedman's solutions of the field equations which proposed expanding or contracting space.

*Heikki Sipilä, "The Zero-energy Principle as a Fundamental Law of Nature", La Nuova Critica, Special Issue 63-64, ISSN 1824-9663 (2016), Scientific Models and a Comprehensive Picture of Reality, pp. 29-33.

Dennis Sciama, 1953

In his lectures on inertia, Sciama states: “… Equation implies that the total energy (inertial plus gravitational) of a particle at rest in the universe is zero ... ... if local phenomena are strongly coupled to the universe as a whole, then local observations can give us information about the universe as a whole”.

Sciama did not enter mathematical formulations or further considerations of the zero-energy principle.

Richard Feynman, 1960's

In his lectures on gravitation in 1960's, Richard Feynman stated the total zero-energy condition in space:

“If now we compare the total gravitational energy E(g) = GM(total)^2/R to the total rest energy of the universe, E(rest) = M(tot)c^2, lo and behold, we get the amazing result that GM(total)^2/R = M(total)c^2, so that the total energy of the universe is zero. — It is exciting to think that it costs nothing to create a new particle, since we can create it at the center of the universe where it will have a negative gravitational energy equal to M(tot)c^2. — Why this should be so is one of the great mysteries — and therefore one of the important questions of physics. After all, what would be the use of studying physics if the mysteries were not the most important things to investigate.”

In the same lectures he pondered the possibility of spherically closed space (page p. 164):

"...One intriguing suggestion is that the universe has a structure analogous to that of a spherical surface. If we move in any direction on such a surface, we never meet a boundary or end, yet the surface is bounded and finite. It might be that our three-dimensional space is such a thing, a tridimensional surface of a four sphere. The arrangement and distribution of galaxies in the world that we see would then be something analogous to a distribution of spots on a spherical ball.”

Feynman did not proceed to a solution of the "great mystery" of the zero-energy universe or the "intriguing suggestion" of spherically closed space. Obviously, any solution had infringed general relativity and the space-time concept; for keeping the gravitational energy and the rest energy of matter in balance, the zero-enrgy solution links the expansion of space to a decreasing velocity of light.